1. Field
The present disclosure relates generally to aircraft and, in particular, to detecting icing conditions for an aircraft. Still more particularly, the present disclosure relates to a method and apparatus for detecting ice on the surface of an aircraft.
2. Background
In aviation, icing conditions in the atmosphere may lead to the formation of ice on the surfaces of the aircraft. Further, this ice also may occur within the engine. Ice forming on the surfaces of the aircraft, on the inlets of an engine, and other locations is undesirable and potentially unsafe for operating the aircraft.
Icing conditions may occur when drops of supercooled liquid water are present. In these illustrative examples, water is considered to be supercooled when the water is cooled below the stated freezing point for water but is still in a liquid form. Icing conditions may be characterized by the size of the drops, the liquid water content, the air temperature, and other suitable parameters. These parameters may affect the rate and extent at which ice forms on an aircraft.
When icing occurs, the aircraft does not operate as desired. For example, ice on the wing of an aircraft will cause the aircraft to stall at a lower angle of attack and have an increased level of drag.
Aircraft may have mechanisms to prevent icing, remove ice, or some combination thereof to handle these icing conditions. For example, aircraft may include icing detection, prevention, and removal systems. Ice may be removed using deicing fluid, infrared heating, and other suitable mechanisms.
With respect to detecting ice on the surface of an aircraft, ice detection systems that are currently available may not detect formation of ice on the surface of an aircraft as accurately as desired. With currently used ice detection systems, false indications of ice may occur.
For example, one ice detection system detects moisture and temperature. If moisture is present in the environment around the aircraft and if the temperature is low enough, then the ice detection system indicates that ice is present on the surface of the aircraft. However, in some cases, ice may not actually be present on the surface of that aircraft. Depending on the conditions in the environment, moisture may not form ice until temperatures that are lower than the temperatures used as a threshold to indicate a presence of ice are present. Thus, inaccurate indication of a presence of ice may occur.
Further, both small and large supercooled droplets may accumulate on the surface of the aircraft. The accumulation of each type of supercooled droplet may require different safety considerations. For example, when large supercooled droplets accumulate on the aircraft, those droplets may become a safety concern for the safe flight of the aircraft. With small supercooled droplets, those droplets may accumulate on the forward edges of the aircraft without becoming as much of a safety concern to the flight of the aircraft. Current ice detection systems may not differentiate between small and large supercooled droplets. Thus, inaccurate information about the type and severity of ice may occur.
Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues.